The invention is directed generally to throttle valves used in air intake systems for internal combustion engines. More particularly, it relates to the interaction between, and construction of, the throttle plate (or butterfly) and throttle shaft, so that as a unit they resist bending to a greater extent than current butterfly and shaft combinations.
This invention concerns a throttle valve construction for automotive engines. Throttle valves typically comprise a butterfly or throttle plate attached to a throttle shaft extending across the bore of a throttle body controlling inlet airflow to the intake manifold.
The throttle shaft is rotated to control the airflow by variably restricting the throttle bore with the throttle plate by rotating the throttle shaft.
While metal, in particular steel and aluminum, have been the preferred construction materials in the past, fiber filled or reinforced thermoplastics have been lately considered as replacements, for example high temperature Nylon 66 filled with glass fibers for reinforcement.
Thermoplastics are generally not as strong as metals and suffer from high temperature creep. Thermoplastic components also tend to deflect under the pressure differentials that are generated across the butterfly in modern internal combustion engines. To solve this problem, some have proposed making the shaft and butterfly thicker. This, however, blocks the free flow of air through the throttle body in which the valve is installed. In one design, for example, the butterfly has a hollow tube that slides over the shaft when the shaft is inserted. This design, however, provides a large barrier to airflow due to the combined thickness of the shaft and the butterfly tube. In addition, this design requires that the butterfly be positioned within the throttle body and alignied with shaft holes in the throttle body before the throttle shaft can be inserted. Since the butterfly is slid onto the throttle shaft, the tube in the throttle body must have an inside diameter at least as great as the major diameter of the shaft.
It is an object of this invention to provide a throttle shaft and butterfly that when combined resist bending stresses to a greater extent than current designs, based upon the interaction between the throttle shaft and butterfly resisting bending as a unit.
It is an object of the invention to provide a stronger throttle shaft and butterfly that do not block as much of the air flow through the throttle body. It is also an object of this invention to provide a throttle shaft and butterfly that can be assembled by first inserting the throttle shaft into the throttle body and subsequently attaching the butterfly to one side of the throttle shaft.
The above object and others which will become apparent upon a reading of the following specification and claims are achieved by a throttle valve construction in which the throttle shaft component is molded from a plastic composite material, and is formed with a flattened side against which one side of the throttle plate is held. One or more bosses integrally formed projecting from the flattened side of the throttle shaft, are received into corresponding holes in the throttle plate which is also molded from a composite plastic.
One or more ribs are formed in the throttle shaft that extend parallel to the length of the shaft. These shaft ribs are preferably spaced apart and fitted into mating recesses in the butterfly plate.
Ribs may also be provided on an outer surface of the butterfly to strengthen it. These butterfly ribs preferably extend perpendicular to the axis of the shaft from one wing to the other wing of the butterfly.
Viewing the butterfly ribs from the side, they preferably describe an upper surface of an airfoil.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.